Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$148.96	6.647%	$158.8614	$158.86	$158.85	$158.90
Purchase #2	$218.35	11.644%	$243.7747	$243.77	$243.75	$243.80
Purchase #3	$6.28	10.154%	$6.9177	$6.92	$6.90	$6.90
Purchase #4	$175.67	13.585%	$199.5348	$199.53	$199.55	$199.50
Purchase #5	$84.31	5.710%	$89.1241	$89.12	$89.10	$89.10
Purchase #6	$103.99	13.833%	$118.3749	$118.37	$118.35	$118.40
Purchase #7	$144.94	5.199%	$152.4754	$152.48	$152.50	$152.50
7 purchase totals =	$882.50		$969.0630	$969.05	$969.00	$969.10